Actually, if you turn a Maggie so that you're looking at it edge-on (more like you'd have a dipolar surround mounted), then it will put out a very diffuse sound field. Give it a try.

In the normal orientation, the sound coming off the back-side of a Maggie is reflected off another surface before it gets to your ear, so it is no longer perfectly out-of-phase by the time it reaches your ear.